But the united stand among First Nations, grassroots and environmentalists has been met with an equally adamant federal government that appears unwilling to budge, forming the battle lines for an extended conflict.
"Our fights may be different, but our dreams and hopes for our people are common," Spence said in a statement posted Wednesday, thanking Idle No More for bringing awareness to the new environmental laws and urging unity among First Nations.
Prime Minister Stephen Harper, however, is not blinking.
"The government has no plans to reconsider its legislation," the prime minister's spokesman, Andrew MacDougall, said bluntly in an email Wednesday.
While there may be room to negotiate with Ottawa on other issues that have driven First Nations people into the streets in protest, the division over how to handle resource development and the environment is deep and entrenched.
Wednesday's day of action included traffic disruptions and public demonstrations across the country, but remained peaceful. Some chiefs, warn of blockades if material changes aren't made soon. And Spence's liquids-only hunger protest persists.
At issue are two huge and complicated pieces of legislation stemming from last year's budget, of which more efficient natural resource extraction was the centrepiece.
Bill C-38, which passed in June, completely overhauls Canada's environmental assessment law, redefines protections for fish and gives the federal cabinet new decision-making powers on resource development.
Environmentalists and First Nations alike say the changes allow mining and energy companies to steamroll over their concerns, and rush into resource extraction without properly accounting for harm to animal habitats.
But an analysis by lawyers at Fraser Milner Casgrain says the changes also impose new responsibilities on corporations when it comes to dealing with First Nations. Plans for resource extraction will need to take into consideration any effect on aboriginal health, socio-economic conditions, physical and cultural heritage, and historical sites.
C-45, the second omnibus budget bill, received royal assent in December. It overhauls protections of waterways by dramatically changing the Navigable Waters Act, as well as changing the Fisheries Act and the Hazardous Materials Information Review Act.
"Is this the appropriate thing to do for the economy at the expense of future generations?" said Ontario Regional Chief Stan Beardy, protesting Wednesday along with hundreds of others alongside a northern Ontario highway, shouting to be heard over a line of transport trucks slowed by the demonstration.
"We want to have a source of clean drinking water."
Behind the scenes, there may be some wiggle room as the federal government goes about crafting regulations on how to implement C-45. Harper and his officials indicated as much to chiefs who met with him and several cabinet ministers last week, insiders say.
"The PM did say that the law is now passed, but the regulations in many cases still need to be worked out, and that will involve consultation," said one government official, speaking on condition of anonymity.
That's unlikely to do much to assuage the deep concerns shared by environmentalists and First Nations, said Megan Leslie, the NDP environment critic.
"The Conservatives could certainly say we'll add that lake or river to the (protected waters) list," she said. "But that's tinkering around the edges. They (chiefs and protesters) are concerned with the overall omnibus bill."
Still, she said the Conservatives have shown that they will move on legislation if they think it's not right. Included in C-45, for example, were two major changes to the just-passed C-38.
"I think there's absolutely room to figure out what to do here," Leslie said.
Companies need a solution just as much as First Nations and environmentalists, added Anna Baggio, director of conservation land use planning with CPAWS Wildlands League.
Baggio is on the front lines of proposed mining development in northern Ontario, and she sees companies working hard to get the 'social license' they need to obtain First Nations support and go ahead with resource extraction.
If the public does not have confidence in the government's environmental oversight, businesses will find it even more difficult to proceed, she said.
"From a big business standpoint, if the government wants 'responsible resource development', there are things you have to put in place to be sure it is responsible."
But even if Harper stands his ground and does not entertain changes to the two omnibus bills, First Nations have two more cards to play, Beardy said.
For one, the protest movement has only just begun and will amplify once the weather warms up, he said. His northern Ontario group was on the highway for hours Wednesday in -15 C temperatures.
"Something has to be really wrong to do that," Beardy said.
Plus, aboriginal people still have legal rights that will likely trump the most recent federal legislation, he added, pointing to protections of aboriginal rights in the constitution.
Indeed, there is already one lawsuit, with two Alberta First Nations asking for a judicial review of the bills, claiming the federal government did not fulfil its duty to consult with First Nations before passing the legislation.
Forcing First Nations to go to court is not a sustainable response, Leslie said.
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